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CI Cam 前にも関連の話題をちょっと紹介したことがあったと思いますが、こういう論文が 出ています。もし本当に新星と認識されるならば、「新星」の概念がだいぶ広がる かも知れませんね。「新星」かどうかの判断がずっと後まで議論されることがある ことの一例にもなるでしょう。 しかし、RXTEがこの時に検出していなくて（あるいはＸ線衛星がなくて）、可視光で のみ増光が見つかっていたら、当時はどのように判定されたでしょうね。 （Munariあたりが "symbiotic nova" としそうかな ^^;) ＃新星リストの数を１個増やすかどうかは各人の判断で (^^; なお爆発は1998年です === Title: Possibility of a White Dwarf as the Accreting Compact Star in CI Cam (= XTE J0421+560) Authors: Manabu Ishida, Kazuyuki Morio and Yoshihiro Ueda Comments: 20 pages, 5 figures, to appear in the Astrophysical Journal v601, n2, February 1, 2004 issue \\ We present results from ASCA observations of the binary CI Cam both in quiescence and in outburst in order to identify its central accreting object. The quiescence spectrum of CI Cam consists of soft and hard components which are separated clearly at aound 2-3keV. A large equivalent width of an iron Ka emission line prefers an optically thin thermal plasma emission model to a non-thermal power-law model for the hard component, which favors a white dwarf as the accreting object, since the optically thin thermal hard X-ray emission is a common characteristic among cataclysmic variables (binaries including an accreting white dwarf). The outburst spectrum, on the other hand, is composed of a hard component represented by a multi-temperature optically thin thermal plasma emission and of an independent soft X-ray component that appears below 1 keV intermittently on a decaying light curve of the hard component. The spectrum of the soft component is represented well by a blackbody with the temperature of 0.07-0.12keV overlaid with several K-edges associated with highly ionized oxygen. This, together with the luminosity as high as ~1E38 erg/s is similar to a super-soft source (SSS). The outburst in the hard X-ray band followed by the appearance of the soft blackbody component reminds us of recent observations of novae in outburst. We thus assume the outburst of CI Cam is that of a nova, and obtain the distance to CI Cam to be 5-17kpc by means of the relation between the optical decay time and the absolute magnitude. This agrees well with a recent estimate of the distance of 5-9kpc in the optical band. All of these results from the outburst data prefer a white dwarf for the central object of CI Cam. \\ ( http://arXiv.org/abs/astro-ph/0310616 , 359kb)
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